Specifies a resource pool of servers, one of which is assigned to be the current management server and the other serving ...

Specifies a resource pool of servers, one of which is assigned to be the current management server and the other serving as back-up management servers. This parameter requires a resource pool object and returns only the managed computers in that resource pool. 

For information about how to get a resource pool object, type Get-Help Get-SCOMResourcePool.